The present invention relates to a hydraulic brake system including a pedal-operated master cylinder connected to a supply reservoir, a wheel brake which is connected to the master cylinder by way of a brake line, a pump driven by an electric motor and connected to the brake line, and to a method of pressure control implemented in a brake system of this type.
A brake system of this type is disclosed in German patent application No. 41 28 386. The prior art brake system is used for brake slip control and traction slip control. During brake slip control operations, the brake system operates according to the return principle. For traction slip control operations, the pump of the brake system is of the self-priming type and adapted to take in pressure fluid from the supply reservoir by way of a second suction line and the master cylinder. A separating valve in the brake line is an electromagnetically operated valve which is normally open and functions as a pressure limiting valve in its energized condition. When the supply pressure of the pump exceeds a predetermined value, as compared to the master cylinder pressure, pressure fluid discharges through the separating valve to the master cylinder.
When a brake system of this type is also intended to be used for brake management operations, to the effect of not only eliminating brake slip and traction slip but also for ensuring general driving stability control, e.g. during cornering without braking, it is desirable that the supply pressure of the pump is not fixed to a constant differential value between the pressure line and the master cylinder, but is variable in conformity with requirements.